1. Field of the Invention
The described invention relates generally to the field of data communications. More particularly, the invention relates to a method and apparatus for encrypting data that can be used with standard software communication applications using modems.
2. Prior Art
The use of a modem in combination with a standard telephone line is a common method for exchanging data between computer systems. Modems use a standard communication interface that allows modems from different manufacturers to communicate with each other. The "Advanced Technology" command set has also become a defacto standard command language with which computer systems can control a modem. This combination of a standard command language and a standard interface allows modems made by different manufacturers to provide communication capability with computer systems which are also from different manufacturers. This compatibility gives a user the ability to purchase computers and modems based on price and quality considerations only, and therefore is desirable.
Most recently, modems have been developed which operate over cellular networks using standard cellular phones. In addition, AT compatible modems have been developed that operate over the radio network.
The use of a modem with a highly compatible interface creates some security risk, however, because anyone able to detect the signals used by the modems to exchange information can determine the contents of that information. In the past, this security risk has been minimized by the relatively high degree of privacy offered by a standard phone line. The use of cellular telephones as a substitute for traditional telephones, however, has removed this at least somewhat satisfactory degree of security because the signals carrying the information being exchanged are broadcast where they can be detected by anyone so inclined. Thus, the use of a cellular telephone for data communication between computer systems has created the need to make the information transmitted by the cellular telephone unreadable to anyone other than the intended recipient.
The growing presence of mobile computing involving portable computers and wireless data communications poses a considerable threat to corporate security since wireless communications are vulnerable to interceptions. The communications software used with these portables relies on simple passwords to protect access to the network and the login script generally holds the password in plain text. In other words, the stolen portables gives the thief an easy access to the network. Even some applications that use encryption do not employ a strong encryption scheme.
Encryption provides one method for making the information transmitted by modems unreadable to anyone other than the intended recipient. While modems that provide encryption capability exist, the encryption feature cannot be utilized unless the receiving modem also possesses the same encryption capability. This requirement eliminates much of the desired compatibility previously offered by modems that did not posses encryption capability. Additionally, this hardware-based solution adds to the cost of the modem. Alternatively, communication software programs may incorporate an encryption feature, however, this requires the two computer systems communicating with each other to utilize communication software applications that incorporate the same encryption method. Once again, this reduces users choices and eliminates the previously established compatibility among computer systems. Thus, it is desirable to have a method and apparatus of encrypting data that allows various standard computer systems, software applications, and modems to be used interchangeably and which can be uniformly applied with modems that operate over cellular networks, radio networks and regular telephone lines.